Oversized boiler solution (radiant heat)?

Hello everyone (once again),
I am in the early stages of planning a home conversion from radiator heat to in-floor radiant heat. I have the entire system planned out already- with one big exception- the boiler.
I have a large, 140,000 BTU/hr boiler that's from the mid 90's. Hy home's heat loss calculation is about 40-50,000 BTU/Hr, so the boiler is considerably oversized. My heating bills in the winter time are pretty ridiculous currently ($200-300, and I like it cold; St. Louis, 2000 sq.ft.). I want to keep the same boiler since a new one would be prohibitively expensive. I have noticed that the original boiler installation is shabby at best- there is 1" black pipe that runs to the boiler, and then there is a reducer to 1/2" to feed the boiler. Also, none of the pipe is supported against the wall or joists (!).
Anyway, I thought of the following as a potential way to save some money. Could I underfeed the boiler by replacing the 1" pipe with 1/2" pipe, thereby starving the boiler and prohibiting crazy gas use? Or would the boier be so inefficient that it would end up costing more? I know I will save with the in-floor heat, especially when I replace the HUGE 3" pipes running to the radiators, but I can't afford too want winters like this.

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Oversized boiler solution (radiant heat)?

You need a new boiler. You would have to change the burner orifices and the boiler needs proper sized piping and flow of water or it will overheat etc. Run it too cool and moisture will condense inside the flue passages etc and corrode everything. Mechanically impossible to do what you want to do. Sorry
Check with your local utilities and see if there are any rebates for going to a more efficient boiler. Weil McLain are very good.